LP55231: This chip NACKs the very first transaction after the powerup

Hello,

LP55231 chip on our board does not reply to the very first I2C access after the powerup.  

Our initialization sequence is as follows:

1. Turn on the power
2. Pull EN pin high
3. Delay 500uS
4. Write 0x0040 (CHIP_EN high) to register 0

The problem is that the chip does not ACK the address of the very first transaction.  Every subsequent transaction works just fine.

Have you ever seen anything like this?  What could be the problem?

Thank you in advance.